The present invention relates to a method and apparatus for reducing the concentration of contaminants or impurities entrained in steam, where the contaminants are selected from the group consisting of acid gases and inert particulates. More particularly, the invention relates to removing such contaminants from geothermal steam prior to extracting energy from the steam, e.g., prior to passing the steam through a turbine for the purpose of generating electricity.
Water washing is commonly employed to remove impurities from geothermal steam and thereby protect turbines from fouling (e.g., due to scale formation) and corrosion (e.g., due to the presence of acidic gases in the steam). However, water washing has its drawbacks. For example, water washing requires significant volumes of wash water to scrub the impurities from the steam. In addition, water washing quenches the steam and thus adversely reduces steam utilization and power generation. Furthermore, excessive water washing can send droplets to the turbine causing erosion damage to nozzles and blades. Also, aerated condensate, which is typically employed in water washing, introduces oxygen into the turbine and causes additional corrosion.